Braking apparatus

ABSTRACT

An apparatus for braking a rotating member having an engaged state and a disengaged state is disclosed. Rotation of the rotating member is inhibited by the apparatus when the apparatus is in the engaged state. The braking apparatus includes a housing, an actuator, and a first brake structure. The first brake structure includes a brake pad having a contact surface. The brake structure is pivotally connected to the housing and further connected to the actuator. The actuator is operable to cause pivotal motion of the brake structure, thereby causing arcuate motion of the contact surface toward the rotating member. The frictional force between the rotating member and the contact surface causes further arcuate motion of the contact surface toward the rotating member and places the apparatus in the engaged state.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.09/145,685, filed Sep. 2, 1998 is now U.S. Pat. No. 6,135,243.

GOVERNMENT LICENSE

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms, as provided by the terms of GovernmentContract DTMA 91-95-H-00075, awarded by the U.S. Department ofTransportation, Maritime Administration.

FIELD OF THE INVENTION

The present invention relates generally to a braking apparatus, and morespecifically to a braking apparatus for braking a rotating member.

BACKGROUND OF THE INVENTION

Braking apparatus are employed to inhibit motion in various devices thathave rotating members. One such device is a robot, which may employ abraking apparatus to inhibit motion of the robot arm.

In particular, robots typically include a robot arm to move a work toolbetween various locations where work operations are performed on a workpiece. To move the robot arm, the robot includes a motor that providesrotational motion through a shaft. Linkages or other structures withinthe robot convert such rotational motion into desired movement of therobot arm. To stop the robot arm in a particular position, precise motorcontrol is used. While precise motor control is typically sufficient tostop and hold the robot arm in position, a brake is also required by therobot to hold a robot arm in position either in an emergency stop orduring a power interruption.

More specifically, upon the loss of electrical power due to theinitiation of an emergency stop or an accidental power loss the robotarm must be stopped and held in position by means other than motorcontrol. Stopping and holding the robot arm in position during theaccidental loss of electrical power prevents the robot from damaging thework piece or injuring a technician working in close proximity to therobot arm. Because the control signals which cause the motor to hold therobot arm in position are absent without electrical power, it isnecessary that a braking mechanism be employed to stop and hold therobot arm in the event of a power loss. The braking mechanism can alsobe used to stop and hold the robot arm in position when the electricalpower is purposefully removed from the motor, such as during routinemaintenance of the robot.

In a conventional braking apparatus, such as the disk brakes used inautomobiles, a rigid brake pad is urged into contact with a rotatingmember attached to the shaft. Contact between the rigid brake pad andthe rotating member creates a frictional force which slows the rotationof the rotating member and, thus, the shaft. In order to rapidly stopthe shaft, a relatively large force must be applied to the brake pad.Additionally, to enable fail safe operation, this large force must beprovided by a biasing member, such as a spring, which does not requireelectrical power. This biasing member is operable to urge the brake padinto contact with the rotating member in the event of a power loss.

The robot arm also includes a brake actuator which is operable toovercome the relatively large force of the biasing member when it isdesired to allow movement of the robot arm. Because the brake actuatormust overcome the large bias force, a relatively large and powerfulbrake actuator must be provided. Accordingly, one drawback to using aconventional braking apparatus is that a relatively large and bulkyactuator must be carried in the robot arm, which undesirably increasesthe size and weight of the robot arm. Increasing the size of the robotarm inhibits the maneuverability of the robot arm in confined spaces,and may limit the type of work operations performed by the robot.Moreover, the increased weight of the robot arm may require a morepowerful motor, thereby raising the cost of the robot.

What is needed therefore is an apparatus and method for braking a robotarm which rapidly stops and holds the robot arm in position during theloss of electrical power without significantly increasing the size orweight of the robot arm.

SUMMARY OF THE INVENTION

The present invention addresses the above needs, as well as others, byproviding a method and apparatus for braking a robot arm that employselastically deformable brake pads that are engaged using a pivotalmotion. The elastically deformable brake pads pivot toward a rotatingmember in the direction of the rotation such that frictional forcesbetween the rotating member causes the brake pad to bind the rotatingmember. As a result, a large stopping or braking force may be providedwith less biasing force, thereby facilitating the use of a relativelysmall and light weight brake actuator.

In accordance with a first embodiment of the present invention, there isprovided an apparatus for braking a rotating member. The apparatus hasan engaged state and a disengaged state, wherein rotation of therotating member is inhibited by the apparatus when the apparatus is inthe engaged state. The braking apparatus includes a housing, anactuator, and a first brake structure. The first brake structureincludes a brake pad having a contact surface. The brake structure ispivotally connected to the housing and further connected to theactuator. The actuator is operable to cause pivotal motion of the brakestructure, thereby causing arcuate motion of the contact surface towardthe rotating member. The frictional force between the rotating memberand the contact surface and elastic deformation of one of the rotatingmember and the contact surface causes further arcuate motion of thecontact surface toward the rotating member and places the apparatus inthe engaged state.

In accordance with a second embodiment of the present invention, thereis provided an apparatus for braking a rotating member. The apparatushas an engaged state and a disengaged state wherein rotation of therotating member is inhibited by the apparatus when the apparatus is inthe engaged state. The apparatus includes a housing, an actuator, and afirst brake structure. The first brake structure includes a brake padwhich is elastically deformable and having a substantially convexcontact surface. The brake structure is pivotally connected to thehousing and further connected to the actuator. The actuator is operableto cause pivotal motion of the brake structure, thereby causing arcuatemotion of the contact surface toward the rotating member so as to placethe apparatus in the engaged state.

This invention has the advantage of using pivotal motion to move anelastically deformable brake pad into contact with a rotating member.The resultant self-binding action of the brake pad allows the frictionalforces to increase the rate at which the rotating member is braked.Optionally, the present invention may further employ two opposing pairsof such brake pads. One pair of brake pads are oriented to stop andretain the rotating member when the rotating member is rotating in afirst direction and the opposing pair of brake pads are oriented to stopand retain the rotating member when the rotating member is rotating in asecond direction.

The above features and advantages, as well as others, will becomereadily apparent to those of ordinary skill in the art by reference tothe following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary embodiment of a brakingapparatus according to the present invention;

FIG. 2 is a exploded view of the braking apparatus of FIG. 1;

FIG. 3 is a bottom elevational view of the braking apparatus of FIG. 1,note that the braking apparatus is positioned in the disengaged state;

FIG. 4 is a view similar to FIG. 3, but showing the braking apparatuspositioned in the engaged state;

FIG. 5A is a enlarged side elevation view of a brake pad prior toengaging the rotating member;

FIG. 5B is a view similar to that shown in FIG. 5A but showing the brakepad engaging the rotating member; and

FIG. 5C is a view similar to that shown in FIG. 5B but showing theelastic distortion of the brake pad as the brake pad engages therotating member.

DETAILED DESCRIPTION

While the invention is susceptible to various modifications andalternative forms, a specific embodiment thereof has been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

FIGS. 1 and 2 illustrate an exemplary embodiment of a brake assembly 10according to the present invention. The brake assembly 10 includes ahousing 12 an actuator assembly 39, and first, second, third and fourthbrake structures 16, 18 ,20, and 22, respectively. As discussed furtherbelow, each of the brake structures includes a brake pad such as thebrake pad 86, and each brake pad in turn has a contact surface, such asthe contact surface 94 of the brake pad 86. It should be noted that theterms “actuator” and “actuator assembly” as used herein refer toactuator components of the brake assembly, as opposed to referring tothe robot actuator itself.

In accordance with the present invention, the brake assembly 10alternatively engages a rotating member 90 of a robotic device to stoprotation of the member 90 and disengages the rotating member 90 to allowrotation of the member 90. In particular, to engage the brake assembly10, the actuator assembly 39 causes pivotal motion of each brakestructure, thereby causing arcuate motion of each corresponding contactsurface toward the rotating member 90. Contact between the contactsurface and the rotating member 90 causes elastic deformation of thecorresponding brake pad, or alternatively, the rotating member 90itself. The elastic deformation and the frictional force causes furtherarcuate motion of the contact surface toward the rotating member 90. Thefurther arcuate motion of the contact surface toward the rotating memberresults in a binding force that absorbs rotational energy, therebycausing the rotating member 90 to ultimately stop.

In further detail, each of the brake structures 16, 18, 20, 22 in theexemplary embodiment described herein further includes a pivot pin 26and an actuation pin 28. The pivot pin 26 of each of the respectivebrake structures 16, 18, 20, 22 is received through one of a pluralityof pin apertures 14 defined in the housing 12 (see FIG. 2). Each pivotpin 26 is secured to the housing 12 by a fastener, such as the clip 30.The clip 30 prevents the brake structures 16, 18, 20, 22 from moving inthe general directions of arrows 32 and 34 while allowing pivotal motionof each of the brake structures 16, 18, 20, 22 relative to the housing12 about their respective pivot pin 26.

The housing 12 in the exemplary embodiment described herein furtherincludes four guide slots 40 (shown in FIG. 2) defined therein. Theactuation pin 28 of each of the brake structures 16, 18, 20, and 22 isreceived through a corresponding guide slot 40. In particular, as thepivot pin 26 of a respective brake structure 16, 18, 20, 22 is receivedthrough the pin aperture 14, the actuation pin 28 of the same brakestructure 16, 18, 20, 22 is received through the respective guide slot40. It should be appreciated that the guide slot 40 of each brakingmember 16, 18, 20, 22 restricts the range of pivotal motion of therespective brake structure 16, 18, 20, 22 about the corresponding pivotpin 26 in the general direction of arrows 36 and 38.

FIGS. 3 and 4 show bottom elevational views of the braking assembly 10of FIG. 1. As will be discussed further below, FIG. 3 shows the brakingassembly 10 in the disengaged state, and FIG. 4 shows the brakingassembly 10 in the engaged state.

Referring again to FIGS. 1 and 2, the actuator assembly 39 in theembodiment described herein includes a cross linkage 41, a first spring64, a second spring 66, a drive plate 62, a solenoid 74 and a manualoverride plate 80. In general, the cross linkage 41 and the first andsecond springs 64 and 66 form a spring biased linkage. As discussedbelow, the spring biased linkage formed by the cross linkage 41 and thesprings 64 and 66 biases the contact surfaces 94 of the brake structures16, 18, 20 and 22 toward the rotating member 90.

In further detail, the cross linkage 41 of the exemplary actuatorassembly 39 described herein interconnects the actuator pins 28 of eachof the brake structures 16, 18, 20, and 22. To this end, the crosslinkage 41 includes a first lever 42 and a second lever 44. Both thefirst lever 42 and the second lever 44 are pivotally secured to anaperture 47 (shown in FIG. 2) of the housing 12.

In particular, a pivot aperture 46 (shown in FIG. 2) is defined near thecenter point of the first lever 42, and a pivot aperture 48 (shown inFIG. 2) is defined near the center point of the of the second lever 44.A fastener, such as a bolt 50 is inserted through both the pivotaperture 48 of the second lever 44 and the pivot aperture 46 of thefirst lever 42, and is then secured to the housing 12. It should beappreciated that securing the first lever 42 to the housing 12 with thebolt 50 allows the first lever 42 and the second lever 44 to pivot aboutthe bolt 50 in the general direction of arrows 36 and 38.

In addition, the first lever 42 includes a first pin slot 52 definedthrough one end and a second pin slot 54 defined through the opposingend. The actuation pin 28 of the first brake structure 16 is receivedthrough the first pin slot 52 whereas the actuation pin 28 of the thirdbrake structure 20 is received through the second pin slot 54.

In a similar fashion, the second lever 44 includes a first pin slot 56defined through one end and a second pin slot 58 defined through theopposing end. The actuation pin 28 of the second brake structure 18 isreceived through the first pin slot 56 whereas the actuation pin 28 ofthe fourth brake structure 22 is received through the second pin slot58.

The first spring 64 and the second spring 66 of the exemplary embodimentof the actuator assembly 39 described herein provide spring biasing tothe cross linkage 41 to allow the brake assembly 10 to be normallyengaged. To this end, one end of the first spring 64 is attached to theactuator pin 28 of the first brake structure 16 whereas the other end ofthe first spring 64 is attached to the actuator pin 28 of the secondbrake structure 18.

In a similar manner, one end of the second spring 66 is attached to theactuator pin 28 of the fourth brake structure 22 while the other end ofthe second spring 66 is attached to the actuator pin 28 of the thirdbrake structure 20.

The drive plate 68 of the exemplary embodiment of the actuator assembly39 described herein provides a drive mechanism through which movement ofthe springloaded cross linkage 41 may be controlled. The drive plate 68is operatively housed in the housing 12 such that the drive plate 68 isfree to translate in the general direction of arrows 60 and 62. Thehousing 12 inhibits movement of the drive plate 68 in the generaldirections of arrows 70 and 72. The drive plate 68 has a first driveaperture 75 (shown in FIG. 2) and a second drive aperture 77 (shown inFIG. 2) defined therein. The drive plate 68 is interposed between thehousing 12 and each of the first lever 42 and the second lever 44, priorto the assembly of the linkage 41. In particular, the actuation pin 28of the second brake structure 18 is received through the first driveaperture 75 of the drive plate 68 before being received through thefirst pin slot 56 of the second lever 44 whereas the actuation pin 28 ofthe third brake structure 20 is received through the second driveaperture 77 of the drive plate 68 before being received through thesecond pin slot 54 of the first lever 42.

The first drive aperture 75 and the second drive aperture 77 are equallydistant from the bolt 50. Accordingly, movement of the drive plate 68 inthe general direction of arrow 62 causes the first lever 42 to rotate inthe general direction of arrow 38 an amount substantially identical tothe amount the second lever 44 rotates in the general direction of arrow36. The bias force of the first spring 64 acting on the actuation pin 28of the second brake structure 18 and the bias force of the second spring66 acting on the actuation pin 28 of the third brake structure 20 bothact to urge the drive plate 68 in the general direction of arrow 60.

The solenoid 74 of the exemplary embodiment of the actuator assembly 39described herein is secured to the housing 12. The solenoid 74 includesa plunger 76. The end of the plunger 76 is secured to the drive plate68. The plunger 76 is operable to move in the general direction ofarrows 60 and 62 in response to a signal from a control unit, not shown.

The manual override plate 80 of the exemplary actuator assembly 39described herein is operatively housed in the housing 12 such that themanual override plate 80 is free to translate in the general directionof arrows 60 and 62. The housing 12 inhibits movement of the manualoverride plate 80 in the general directions of arrows 70 and 72. Themanual override plate 80 has a first plate aperture 82 (shown in FIG. 2)and a second plate aperture 84 (shown in FIG. 2) defined therein. Themanual override plate 80 is interposed between the housing 12 and eachof the first lever 42 and the second lever 44 prior to the assembly ofthe linkage 41. In particular, the actuation pin 28 of the first brakestructure 16 is received through the first plate aperture 82 of themanual override plate 80 before being received through the first pinslot 52 of the first lever 42 whereas the actuation pin 28 of the fourthbrake structure 22 is received through the second plate aperture 84 ofthe drive plate 68 before being received through the second pin slot 58of the second lever 44.

It should be appreciated that first plate aperture 82 and the secondplate aperture 84 are equally distant from the bolt 50 such thattranslation of the manual override plate 80 in the general direction ofarrow 60 causes the first lever 42 to rotate in the general direction ofarrow 36 an amount substantially identical to the amount the secondlever 42 rotates in the general direction of arrow 38. It should furtherbe appreciated that the bias force of the first spring 64 acting on theactuation pin 28 of the first brake structure 16 and the bias force ofthe second spring 66 acting on the actuation pin 28 of the fourth brakestructure 20 both act to urge the manual override plate 80 in thegeneral direction of arrow 62.

It will be noted that the configuration of the actuator assembly 39shown in FIGS. 1-4 and discussed above is given by way of example only.Those of ordinary skill in the art may readily devise alternativeactuators operable to cause the pivotal motion of the brake structuresdiscussed herein. Such alternative embodiments, though different, wouldnevertheless provide many of the advantages of the present invention.

The break assembly 10 preferably further includes means for generatingan electrical signal indicative of whether the brake assembly 10 is inthe engaged or disengaged state. For example, the brake assembly 10 ofFIGS. 1 and 2 further include a contact switch 78 and a correspondingdrive plate extension 79. The contact switch 78 is mounted on thehousing 12. The drive plate extension 79 is advantageously positioned toactuate the contact switch 78 when the brake assembly 10 is in thedisengaged state and to release the contact switch 78 when the brakeassembly 10 is in the engaged state. Other arrangements for generating asignal indicative of the state of the brake assembly 10 may readily beused.

In operation, the brake assembly 10 is spring biased in the engagedstate. FIG. 3 shows the brake assembly 10 in the engaged state. In theengaged state, the frictional force between the brake pads 86 of one ormore the brake structures 16, 18, 20 and 22 and the rotating member 90substantially inhibits rotational motion of the rotating member 90. Assuch, the robot arm in which the brake assembly 10 is incorporated issecured in position.

To allow operation of the robot arm, the brake assembly 10 disengages.To this end, the actuator assembly 39 operates to overcome the springbias on the cross linkage 41. In order to re-engage the brake assembly10, the power to the solenoid 74 is interrupted. Specifically, power tothe solenoid 74 may be interrupted by a power failure or by actuation ofa stop button. Upon occurrence of such a power interruption, the brakeassembly 10 engages by removing the force that overcomes the springbias.

While the brake assembly 10 is engaged, it may be necessary to manuallyrotate or adjust the robot arm. To this end, an operator manipulates themanual override 80 which overcomes the spring bias to disengage thebrake assembly 10.

The operation of the braking assembly is now discussed in further detailin reference to FIGS. 1, 2, 3, 4 and 5A-5C.

When no power is provided to the actuator assembly 39, and inparticular, the solenoid 74, the first spring 64 and the second spring66 provide the spring biasing force to the cross linkage 41 to cause thebrake assembly 10 to be normally engaged. (See FIG. 4). To allowrotation of the rotating disk 90, the control unit provides a signal orvoltage to the solenoid 74 that causes the brake assembly 10 todisengage. In particular, referring specifically to FIGS. 1 and 2, whenthe control unit (not shown) provides a voltage to the solenoid 74,windings (not shown) in the solenoid 74 create a magnetic field whichurges the plunger 76 in the general direction of arrow 62. As the forceof the plunger 76 acting upon the drive plate 68 in the generaldirection of arrow 62 overcomes the spring bias forces of the firstspring 64 and the second spring 66, the drive plate 68 moves in thegeneral direction of arrow 62.

Movement of the drive plate 68 in the general direction of arrow 62causes the pivotal motion of the brake structures 16, 18, 20 and 22 awayfrom the rotating member 90.

In particular, movement of the drive plate 68 in the direction of thearrow 62 causes the first lever 42 to pivot about the bolt 50 in thegeneral direction of arrow 38, thereby urging the actuation pin 28 ofthe first brake structure 16 in the general direction of arrow 60. As aresult, the first brake structure 16 in the general direction of thearrow 38, or in other words, pivots away from the rotating member 90.

Moreover, as the first lever 42 also pivots about the bolt 50 in thegeneral direction of arrow 38, the first lever 42 urges the actuationpin 28 of the third brake structure 20 in the general direction of arrow62. As a result, the third brake structure 20 pivots in the direction ofarrow 38, or in other words, away from the rotating member 90.

In addition, movement of the drive plate 68 in the direction of arrow 62causes the second lever 44 to pivot about the bolt 50 in the generaldirection of arrow 36. The second lever 44 thereby urges the actuationpin 28 of the second brake structure 18 in the general direction ofarrow 62, causing the first brake structure 16 to pivot about the pivotpin 26 in the general direction of arrow 36. As a result the secondbrake structure 18 also pivots away from the rotating member 90.

Furthermore, as the second lever 44 pivots about the bolt 50 in thegeneral direction of arrow 36, the second lever 44 urges the actuationpin 28 of the fourth brake structure 22 in the general direction ofarrow 60. As a result, the fourth brake structure 22 pivots in thegeneral direction of arrow 36, or in other words, away from the rotatingmember 90.

Thus, movement of the drive plate 68 causes each of the brake structures16, 18, 20 and 22 to pivot away from the rotating member 90. After thebrake structures 16, 18, 20 and 22 pivot away from the rotating member90, the brake assembly 10 is disengaged and the rotating member 90 isfree to rotate.

At any time during operation of the robot, power may be removed from thesolenoid 74, which causes the brake assembly 10 to engage as describedbelow. Power may be removed from the solenoid 74 as a result of a powerfailure, or through intentional actuation of a stop button, not shown,in the robot work cell. In response to the actuation of the stop button,the control unit stops providing a voltage to the solenoid 74, therebycausing power to be removed from the solenoid 74.

When power to the solenoid 74 is interrupted, the bias force of thefirst spring 64 and the second spring 66 urge the drive plate 68 in thegeneral direction of arrow 60 to return the drive plate 68 to theposition shown in FIGS. 1, 2 and 4. As discussed below, movement of thedrive plate 68 in the direction of the arrow 60 causes engagement of thebrake assembly 10.

In particular, movement of the drive plate 68 in the direction of arrow60 causes the first lever 42 to pivot about the bolt 50 in the generaldirection of arrow 36. The first lever 42 thus urges the actuation pin28 of the first brake structure 16 in the general direction of arrow 62,causing the first brake structure 16 to pivot about the pivot pin 26 inthe general direction of arrow 36. As a result, the first brakestructure 16 pivots toward the rotating member 90.

Contemporaneously, as the first lever 42 pivots about the bolt 50 in thegeneral direction of arrow 36, the first lever 42 urges the actuationpin 28 of the third brake structure 20 in the general direction of arrow60, thereby causing the third brake structure 20 to pivot about thepivot pin 26 in the general direction of arrow 36. As a result, thethird brake structure 20 also pivots towards the rotating member 90.

The movement of the drive plate 68 in the direction of arrow 60 furthercauses the second lever 44 to pivot about the bolt 50 in the generaldirection of arrow 38. The second lever 44 thereby urges the actuationpin 28 of the second brake structure 18 in the general direction ofarrow 60, causing the second brake structure 18 to pivot about the pivotpin 26 in the general direction of arrow 38. As a result, the secondbrake structure 18 pivots toward the rotating member 90.

Contemporaneously, as the second lever 44 pivots about the bolt 50 inthe general direction of arrow 38, the second lever 44 urges theactuation pin 28 of the fourth brake structure 22 in the generaldirection of arrow 62, causing the fourth brake structure 22 to pivotabout the pivot pin 26 in the general direction of arrow 38. As aresult, the fourth brake structure 22 also pivots towards the rotatingmember 90.

The pivotal motion of the brake structures 16, 18, 20 and 22 toward therotating member 90 causes engagement of the brake assembly 90. To thisend, if the rotating member 90 is rotating in a first direction, thenthe pivotal movement of the first brake structure 16 and the secondbrake structure 18 provides a binding braking action to the rotatingmember 90. Contrariwise, if the rotating member 90 is rotating in asecond direction, then the pivotal movement of the third brake structure20 and the fourth brake structure 22 and provide a binding brakingaction to the rotating member 90. Further detail regarding theinteraction of the brake structures 16, 18, 20 and 22 and the rotatingmember 90 during engagement of the brake assembly 10 is provided belowin connection with FIGS. 5A-5C.

When the brake assembly 10 is in the engaged state, it may occasionallybe necessary for an operator to manually manipulate the robot arm. Tothis end, the operator employs the manual override plate 80 totemporarily disengaged the brake while power is still removed from thesolenoid 74.

In particular, to operate the manual override, an operator grasps andpulls on the manual override plate 80, thereby causing the manualoverride plate 80 to move in the general direction of arrow 60. As theforce applied to the manual override plate 80 overcomes the spring biasforces of the first spring 64 and the second spring 66 in the generaldirection of arrow 60, the cross linkage 41 translates such motion tothe drive plate such that the drive plate 68 moves in the generaldirection of arrow 62. As discussed above, movement of the drive platein the direction of the arrow 62 causes disengagement of the brakeassembly 10.

When the force is removed from the manual override plate 80, the biasforce of the first spring 64 and the second spring 66 urge the manualoverride plate 80 in the general direction of arrow 62 to return thedrive plate 68 to the position shown in FIGS. 1 and 2.

An important feature of the embodiment of the present inventiondescribed herein is the employment of pivotal motion of the brake pads86 combined with plastic deformation of the brake pads 86 to create abinding braking action. Such a binding braking action allows for smallerbrake structures to achieve the same braking ability as much larger,conventional disk-type brake structures.

FIGS. 5A, 5B, and 5C show the advantageous binding action provided bythe brake assembly 10 according to the present invention. To this end,FIGS. 5A-5C show the operation of the first brake structure 16 while thebrake assembly 10 of FIGS. 1 and 2 is the process of engagement. It willbe appreciated that FIGS. 5A-5C show the operation of the first brakestructure 16 apart from the brake structures 18, 20 and 22 for purposesof clarity of exposition.

The first brake structure 16 is located adjacent to an axial firstengagement surface 96 of the rotating member 90, and as shown generallyin FIGS. 1 and 2. The first brake structure 16 is furthermore locatednear the annular edge 97 of the first engagement surface 96 of therotating member 90. The rotating member 90 is illustrated in FIGS. 5A-5Crotates about a shaft 92 in the direction of arrow 100. As a result, theannular edge 97 of the rotating member 90 shown in FIGS. 5A-5C movesfrom right to left.

It is noted that the brake pad 86 in the embodiment described herein iscomposed of a deformable elastic material such as a rubberized plastic.The deformable elastic material behaves such that when stress is appliedto the brake pad 86, the brake pad 86 will elastically deform. When thestress is removed from the brake pad 86, the brake pad 86 willsubstantially return to its original shape. In a preferred embodiment ofthe present invention, the brake pad 86 includes a convex contactsurface 94.

Referring specifically to FIG. 5A, the exemplary first brake structure16 is shown in disengaged state. As described above, the brake assembly10 is disengaged when the drive plate 68 or the manual override plate 80provides the force that overcomes the bias force of the first spring 64and second spring 66 (shown in FIGS. 1 and 2). As shown in FIG. 5A, theresulting net force is applied to the actuation pin 28 in the generaldirection of arrow 87, placing the brake pad 86 out of contact with therotating member 90.

Upon engagement of the brake assembly 10, the bias force of the crosslinkage 41 (shown in FIGS. 1 and 2) provides a force to the actuationpin 28 in a first axial direction with respect to the rotating member90, shown by the arrow 88. Such a force causes the brake pad 86 to movealong an arcuate path in the general direction of arrow 36. Arcuatemotion of the first brake structure 16 thus moves the convex contactsurface 94 of the brake pad 86 in the first axial direction with respectto the rotating member 90. The convex contact surface 94 continues tomove in the first axial direction, and at some point makes initialcontact with the first engagement surface 96 as shown in FIG. 5B.

As shown in FIG. 5C, after further pivotal movement of the brake pad 86(and consequent movement of the contact surface 94 in the first axialdirection), friction between the contact surface 94 of the brake pad 86and the engagement surface 96 of the rotating member 90 creates africtional force in the general direction of arrow 98. The frictionalforce is proportional to the normal force in the direction of arrow 95between the brake shoe 86 and the rotating member 90. Moreover, thefrictional force applied in the general direction of arrow 98 creates amoment about the pivot pin 26 that causes further arcuate motion of thefirst brake structure 16 in the general direction of arrow 36. Thefurther arcuate motion of the first brake structure 16 increases thenormal force in the general direction of arrow 95 between the firstbrake structure 16 and the rotating member 90, which further increasesthe frictional force in the general direction of arrow 98. The increasedfrictional force further increases the moment about the pivot pin 26which cause yet further arcuate motion of the first brake structure 16in the general direction of arrow 36.

Furthermore, elastic material from the substantially convex contactsurface 94 of the brake pad 86 is drawn in the general direction ofarrow 72 by the frictional force in the general direction of arrow 98,thus increasing the amount of material between the pivot pin 26 and therotating member 90 and elastically deforming the shape of the brake pad86. Increasing the amount of material between the pivot pin 26 and therotating member 90 increases the normal force in the general directionof arrow 95 exerted by the first brake structure 16 on the engagementsurface 96 of the rotating member 90. As a result, the frictional forcein the general direction of arrow 98 increases, thereby furtherincreasing the arcuate motion of the first brake structure 16. Theresultant self-feeding normal force created by the frictional force andthe cooperative motion of the elastic brake pad 86 causes the rotatingmember 90 to stop.

As a result, the first brake structure 16 of the present inventionemploys a binding braking action in which the first brake structure 16is engaged to the rotating member 90 such that the rotating member 90 isinhibited from further rotational movement in the general direction ofarrow 100. The rapid binding caused by the accumulation of elasticmaterial of the brake pad 86 against the rotating member 90 is anadvantage in robot applications because it provides a greater brakingforce than available from ordinary non-elastic brakepads moved in anormal direction with respect to the rotating member.

Although not shown in FIGS. 5A-5C, it is noted that the second brakestructure 18 operates in a manner similar to the first brake structure16. The second brake structure 18, however, is disposed adjacent thesecond engagement surface of the rotating member 90. The second brakestructure 18 is nevertheless aligned corresponding to the first brakestructure 16 with respect to the annular edge 97 (see FIGS. 1, 3 and 4).Accordingly, in operation, the second brake structure 18 moves itscorresponding convex contact surface in a second axial direction towardthe second engagement surface of the rotating member (See generallyFIGS. 3 and 4). The use of the second brake structure 18 aligned withthe rotating member 90 in a position corresponding to the position ofthe first brake structure 16 provides smooth braking operation byproviding more or less equivalent forces to be applied to oppositeengagement surfaces of the rotating member 90.

It is noted that the first brake structure 16 and second brake structure18 provide the binding braking action in part because they are disposedin such a manner as to pivot generally in the direction of the rotationof the rotating member 90. In particular, as shown in FIG. 5A-5C, thefirst brake structure 16 engages the rotating member 90 by pivoting inthe direction of the arrow 36, which is generally consistent with theright-to-left movement of the annular edge 97 of the rotating member 90near which it is located. Likewise, as discussed above in connectionwith FIGS. 1 and 2, the second brake structure 18 moves generally in thedirection of arrow 38, which, because it is disposed to engage thesecond engagement surface (or the opposite side) of the rotating member90, is also consistent with the movement of the rotating member 90 shownin and described in connection with FIGS. 5A-5C.

It is further noted that if the rotating member 90 rotates in theopposite manner, for example, consistent with the arrow 99 in FIGS.5A-5C, then the first brake structure 16 and second brake structure 18do not provide a binding braking action. In particular, the frictionalforces between the contact surfaces 94 of the first and second brakestructures 16 and 18 tend to urge the first and second brake structures16 and 18 to pivot away from the rotating member 90.

However, the third brake structure 20 and the fourth brake structure 22,configured as described above in connection with FIGS. 1, 2, 3 and 4,provide the binding braking action when the rotating member 90 isrotating in the opposite direction as that described in connection withFIGS. 5A-5C.

In particular, the third brake structure 20 is advantageously configuredto operate as an opposing brake structure to the second brake structure18. By “opposing”, it is meant that the third brake structure 20 pivotsin the opposite direction as the second brake structure 18, yet engagesthe same second engagement surface of the rotating member 90 as thesecond brake structure 18. Because the third brake structure 20 pivotsin the opposite direction as the second brake structure 18, the thirdbrake structure 20 provides the binding braking action described abovein connection with FIGS. 5A-5C when the rotating member 90 is rotatingin the opposite direction.

In a similar manner, the fourth brake structure 22 constitutes anopposing brake structure to the first brake structure 16. As a result,fourth brake structure 22 provides binding braking action similar to thefirst brake structure 16, but only when the rotating member 90 isrotating in the direction opposite to that shown in and described inconnection with FIGS. 5A-5C.

The four brake structures 16, 18, 20 and 22 provide additionaladvantages over the prior art by allowing a pair of brake pads 86 tobind the rotating member 90 rotating in either direction. The firstbrake structure 16 and the second brake structure 18 bind the rotatingmember 90 when the rotating member 90 is rotating in the generaldirection of arrow 99 while the third brake structure 20 and the fourthbrake structure 22 bind the rotating member 90 when rotating in thegeneral direction of arrow 100. Furthermore, the linkage 41 isadvantageously configured that each of the brake structures 16, 18, 20,and 22 rotates an equal amount when binding with the rotating member 90thereby ensuring that the braking apparatus 10 binds the rotating member90 at an equal rate regardless of the rotational direction of therotating member 90.

A further advantage of the braking apparatus 10 is the fail safe mode ofoperation. Due to the spring bias of the first spring 64 and the secondspring 66, the brake structures are biased into the engaged position asshown in FIG. 4. The brake assembly 10 will remain in the engagedposition until acted on by an outside force. The first outside forcethat will disengage the braking apparatus 10 is the movement of thedrive plate 68 by the solenoid plunger 76 in the general direction ofarrow 62. During movement of the robot arm, a voltage is applied to thesolenoid 74 such that the plunger 76 is pulled in the general directionof arrow 62. To brake the robot arm, a controller removes the voltagefrom the solenoid 74 to engage the braking apparatus 10. In event of apower failure, the voltage is automatically removed from the solenoid 74and the braking apparatus 10 is placed in the engaged position. Thesecond outside force that will disengage the braking apparatus 10 is aforce applied to the manual override plate 80 in the general directionof arrow 60 which places the braking assembly 10 in the disengagedposition.

While the present invention has been illustrated and described in detailin the drawings and foregoing description, such illustration anddescription is to be considered as exemplary and not restrictive incharacter, it being understood that only the preferred embodiment hasbeen shown and described and that all changes and modifications thatcome within the spirit of the invention are desired to be protected.

What is claimed is:
 1. An apparatus for braking a rotating member, theapparatus having an engaged state and a disengaged state whereinrotation of the rotating member is inhibited when the apparatus is inthe engaged state, the apparatus comprising: a solenoid operably coupledto a first brake structure such that the apparatus is in the disengagedstate when activating electrical power is provided to the solenoid; anda manual override mechanism operably coupled to a second brake structuresuch that the apparatus is in the disengaged state when an externalforce is provided to the manual override mechanism; wherein theapparatus is in the engaged state when activating power is absent fromthe solenoid and external force is absent from the manual overridemechanism, and wherein a linkage couples the first brake structure tothe second brake structure such that both the solenoid and the manualoverride mechanism are operable to move the first and second brakestructures.
 2. The apparatus of claim 1 wherein the linkage comprises aspring-loaded linkage.
 3. The apparatus of claim 1 wherein the manualoverride mechanism comprises a manual override plate having at least oneaperture, each of the at least one aperture adapted to receive anactuation pin of one of at least one brake structure.
 4. The apparatusof claim 3 wherein the at least one brake structure further comprises abrake pad operably coupled to the actuation pin.
 5. The apparatus ofclaim 1 further comprising an actuation plate having at least oneaperture, the actuation plate coupled to the solenoid, the at least oneaperture coupled to at least one brake structure.
 6. An apparatus forbraking a rotating member, the apparatus having an engaged state and adisengaged state wherein rotation of the rotating member is inhibitedwhen the apparatus is in the engaged state, the apparatus comprising: afirst device operably coupled to a first brake structure such that theapparatus is in the disengaged state responsive to an electrical signalprovided to the first device; and a manual override mechanism operablycoupled to a second brake structure such that the apparatus is in thedisengaged state when an external force is provided to the manualoverride mechanism; wherein the apparatus is in the engaged state whenthe electrical signal is absent from the first device and external forceis absent from the manual override mechanism, and wherein a linkagecouples the first brake structure and the second brake structure suchthat both the first device and the manual override mechanism areoperable to move the first and second brake structures.
 7. The apparatusof claim 6 wherein the linkage comprises a spring-loaded linkage.
 8. Theapparatus of claim 6 wherein the manual override mechanism comprises amanual override plate having at least one aperture, each of the at leastone aperture adapted to receive an actuation pin of one of at least onebrake structure.
 9. The apparatus of claim 8 wherein the at least onebrake structure further comprises a brake pad operably coupled to theactuation pin.
 10. The apparatus of claim 6 wherein the first deviceincludes an actuation plate having at least one aperture, the at leastone aperture coupled to the at least one brake structure.
 11. Anapparatus for braking a rotating member, the apparatus having an engagedstate and a disengaged state wherein rotation of the rotating member isinhibited when the apparatus is in the engaged state, the apparatuscomprising: a) a housing; b) an actuator including a manual overridemechanism; and c) a first brake structure including a brake pad, thebrake pad having a contact surface, the brake structure being pivotallyconnected to the housing and further connected to the actuator; andwherein the actuator is operable to cause first pivotal motion of thebrake structure, thereby causing arcuate motion of the contact surfacetoward the rotating member, the actuator is further operable to causesecond pivotal motion of the brake structure responsive to an electricalsignal, thereby causing second arcuate motion of the contact surfaceaway from the rotating member, and the manual override mechanism isoperable to cause second pivotal motion of the brake structureresponsive to an external force.
 12. The apparatus of claim 11 whereinthe actuator is further operable to cause pivotal motion of the brakestructure, such that the actuator causes arcuate motion of the contactsurface in a first axial direction with respect to the rotating membertoward the rotating member.
 13. An apparatus for braking a rotatingmember, the apparatus having an engaged state and a disengaged statewherein rotation of the rotating member is inhibited by the apparatuswhen the apparatus is in the engaged state, comprising: a) a housing; b)an actuator; c) a first brake structure including a brake pad, the brakepad having a substantially convex contact surface, the first brakestructure being pivotally connected to the housing and further connectedto the actuator; and wherein the actuator is operable to cause pivotalmotion of the brake structure about an axis that extends in asubstantially radial direction with respect to the rotating member,thereby causing arcuate motion of the contact surface toward anengagement surface of the rotating member so as to place the apparatusin the engaged state.
 14. The apparatus of claim 13 further comprising asecond brake structure including a second brake pad, the second brakepad having a substantially convex second contact surface, the secondbrake structure being pivotally connected to the housing and furtherconnected to the actuator, and wherein the actuator is operable to causepivotal motion of the second brake structure, thereby causing arcuatemotion of the second contact surface in a second axial direction withrespect to the rotating member toward a second engagement surface of therotating member.
 15. The apparatus of claim 13 wherein the actuatorfurther includes a spring-loaded linkage that biases the contact surfacetoward the rotating member, thereby causing arcuate motion of thecontact surface toward the engagement surface of the rotating member.16. The apparatus of claim 15 wherein the actuator further comprises abrake release device coupled to the spring-loaded linkage thatcontrollably urges the contact surface away from the engagement surfaceof the rotating member to place the apparatus in the disengaged state.17. The apparatus of claim 16 wherein the brake release device comprisesa solenoid having a plunger, and wherein the plunger engages thespring-loaded linkage, and overcomes the bias of the spring loadedlinkage thereby causing arcuate motion of the contact surface away fromthe engagement surface of the rotating member.
 18. The apparatus ofclaim 13 further comprising an opposing brake structure including anopposing brake pad, the opposing brake pad having a substantially convexcontact surface, the opposing brake structure being pivotably connectedto the housing and further connected to the actuator, and wherein theactuator is further operable to cause pivotal motion of the opposingbrake structure in the opposite rotational direction of the pivotalmotion of the first brake structure, thereby causing arcuate motion thatmoves the contact surface of the opposing brake pad toward theengagement surface of the rotating member.
 19. An apparatus for brakinga rotating member, the apparatus having an engaged state and adisengaged state wherein rotation of the rotating member is inhibited bythe apparatus when the apparatus is in the engaged state, comprising: a)a housing; b) an actuator; and c) a first brake structure including abrake pad, the brake pad having a contact surface, the brake structureconnected to the actuator, the brake structure further pivotallyconnected to the housing proximate a first end of the contact surface,said pivotal connection defining an axis that is substantially radialwith respect to the rotating member; wherein the actuator is operable tocause motion of the brake structure, thereby causing motion of thecontact surface toward the rotating member, and wherein frictional forcebetween the rotating member and the contact surface causes arcuatemotion of the contact surface about the axis toward the rotating memberand places the apparatus in the engaged state.
 20. The apparatus ofclaim 19 wherein the actuator is further operable to cause pivotalmotion of the brake structure about the defined axis.
 21. The apparatusof claim 19 wherein the actuator is further operable to cause pivotalmotion of the brake structure in a first arcuate direction, and whereinthe frictional force between the rotating member and contact surfacecauses arcuate motion of the contact surface in the first arcuatedirection toward the rotating member.